南亚热带红椎和格木人工幼龄林土壤微生物群落结构特征

Characteristics of soil microbial community structure in two young plantations of Castanopsis hystrix and Erythrophleum fordii in subtropical China

采用氯仿熏蒸浸提法和磷脂脂肪酸法(Phospholipids fatty acid,PLFA)研究了我国南亚热带地区非固氮树种红椎(Castanopsis hystrix)和固氮树种格木(Erythrophleum fordii)人工幼龄林土壤微生物生物量与微生物群落结构特征。结果表明,在旱季和雨季,红椎幼龄林土壤微生物总PLFAs量,细菌PLFAs量、放线菌PLFAs量及丛枝菌根真菌PLFAs量均大于格木幼龄林。红椎幼龄林土壤PLFA Shannon多样性指数(H_(PLFA))在旱季和雨季均大于格木幼龄林。主成分分析表明,土壤微生物群落结构组成受到林分类型和季节的双重影响。冗余分析表明,土壤硝态氮(NO_3^--N)含量、土壤含水量、p H及土壤微生物生物量氮(MBN)与特征磷脂脂肪酸之间呈显著相关关系。以上结果表明固氮树种格木与非固氮树种红椎人工幼龄林对土壤微生物生物量和群落结构的影响存在显著差异。

The effects of two plantation stands of non-N-fixing Castanopsis hystrix and N-fixing Erythrophleum fordii on soil microbial biomass and microbial community structure in south subtropical China were studied by fumigation-extraction and phospholipid fatty acid （PLFA） analyses. The results showed that soil pH, soil N status （total N, NH4＋-N and NO3--N）, soil microbial total PLFAs, bacterial PLFAs, actinomycetes PLFAs and arbuscular mycorrhizal fungi PFLAs were significantly influenced by plantation type and season, while only season significantly influenced soil microbial biomass carbon and fungal PLFAs, but soil microbial biomass nitrogen（MBN） was not significantly affected by plantation type and season. The content of soil NH4＋-N and NO3--N in C. hystrix plantation were significantly higher than those in E. fordii plantation during both the dry and rainy seasons. In addition, the amounts of soil microbial total PLFAs and bacterial, actinomycete, and arbuscular mycorrhizal fungi PFLAs in C. hystrix plantation were significantly higher than those in E. fordii plantation during both the seasons as well. Furthermore, the richness and Shannon diversity index of soil microbial PLFAs were significantly altered by plantation type, Shannon diversity index of soil microbial PLFAs in C. hystrix plantation was significantly higher than that in E. fordii plantation during both the seasons. Principal component analysis indicated that variations in the soil microbial community structure were affected by both the plantation types and seasons. Redundancy analysis of soil microbial community structure and environmental factors showed that NO3-, soil water content, soil pH, and microbial biomass nitrogen had significant correlations with PLFA signatures. Thus, our study results showed significantly different effects of non-N-fixing C. hystrix and N-fixing E. fordii plantation stands on the soil microbial biomass and community structure. Overall, soil pH and N status may be the main factors that could regulate soil microbial biomass and community structure in the studied plantations.